The present invention relates in general to cast steel alloys for railway car components. More specifically, but without restriction to the particular use which is shown and described, this invention relates to an improved Grade B steel composition for use in manufacturing railway car components.
The Association of American Railroads (xe2x80x9cA.A.R.xe2x80x9d) sets forth guidelines requiring manufactured railway components, for example, truck bolsters, side frames, couplers, yokes and draft arms, to satisfy certain mechanical and chemical properties. Consistent with the needs of the railroad industry, the A.A.R. enumerates standards for the chemical composition ranges and the minimum mechanical properties of cast steel railcar components. Some of these steel standards for railcar components are classified broadly into the following categories: Grade A, Grade B, or Grade C steel. For Grade B steel, for example, the A.A.R. requires the following maximum chemical properties: Carbon 0.32%; Manganese 0.90% (Mn 1.20% when using the carbon reduction allowance); Silicon 1.50%; Phosphorus 0.04%; and Sulfur 0.04%. The A.A.R. also requires for Grade B steel the resulting composition to exhibit the following mechanical properties: Ultimate Tensile Strength 70 KSI; Yield Strength 38 KSI; Elongation 24.0%; Reduction of Area 36.0%; and Charpy Impact values of 15 ft-lbs minimum at +20xc2x0 F. These chemical and mechanical properties for Grade B steel are the minimally tolerable requirements for this grade of steel for the railway parts, assemblies and components manufactured under the A.A.R. specifications. However, depending on the application and customer needs, it is often desirable for Grade B steel railway components with improved strength and enhanced weldability. To this end, other alloys may be added to the above constituent alloy components to enhance the overall performance of the steel and still meet the A.A.R. minimum requirements.
Accordingly, an object of the present invention is to provide an enhanced Grade B steel for casting railcar components, such as truck bolsters and side frames, which meets the A.A.R. chemical specifications for Grade B steel yet exhibits better overall mechanical properties.
Briefly stated, the present invention involves a cast steel alloy which has the following chemical composition, by weight %: Carbon 0.18 to 0.25%; Manganese 0.90 to 1.10%; Phosphorus 0.02% (maximum); Sulfur 0.015% (maximum); Silicon 0.30 to 0.60%; Nickel 0.50% (maximum); Chromium 0.20 to 0.35%; Molybdenum 0.08 to 0.12%; Aluminum 0.03 to 0.08%; Vanadium 0.08 to 0.12%; and residual components, such as, Calcium 0.0 to 1.0 lb per ton. In the normalized state, the resulting composition exhibits the following mechanical properties: Ultimate Tensile Strength 85 KSI (minimum); Yield Strength 50 KSI (minimum); Elongation 24.0% (minimum); Reduction of Area 36.0% (minimum) and Brinell Hardness range 137-208. The aforementioned chemical composition satisfies the A.A.R. specifications for Grade B steel and exhibits better mechanical properties, such as higher yield and tensile strengths. The resulting composition also exhibited Charpy Impact values that meet the A.A.R. Grade B minimum of 15 ft-lbs at +20xc2x0 F. while having the higher yield and tensile strengths. Secondary benefits of the inventive steel composition include better weldability
The full range of objects, aspects and advantages of the invention are only appreciated by a full reading of this specification and a full understanding of the invention. Therefore, to complete this specification, a detailed description of the invention and the preferred embodiments follow.